Appliances used in drying or air heating applications, such as, for instance, paper machines, agricultural grain dryers, tissue machines, and food and beverage (e.g., beer) processing machines, may utilize fuel (e.g., gas) to perform their operations. The air-fuel or oxygen-fuel ratios of such appliances may be controlled to reduce the pollutant emissions of the appliances and/or increase the efficiency of the appliances. However, any change in the quality (e.g., calorific value) of the gas being supplied to the appliances may increase the pollutant emissions of the appliances and/or decrease the efficiency of the appliances, and hence may necessitate an adjustment of the air-fuel or oxygen-fuel ratios of the appliances.
One approach to determining the quality of the gas being supplied to the appliances, and hence whether to adjust the air-fuel or oxygen-fuel ratios of the appliances, can include installing a calorimeter directly upstream of each different appliance (e.g., at the point the gas is input into each appliance). However, calorimeters can be expensive, which can make such an approach cost-prohibitive.
Another approach to determine whether to adjust the air-fuel or oxygen-fuel ratios of the appliances can include installing a gas sensor to measure the composition of the combustion products (e.g., the percent oxygen in the fumes) of the appliances. However, the combustion products of the appliances may be diluted, and therefore may not provide an accurate indication of the quality of the gas being supplied to the appliances.